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Reasoning system for reasoning with uncertainty

  • US 4,860,213 A
  • Filed: 10/01/1987
  • Issued: 08/22/1989
  • Est. Priority Date: 10/01/1987
  • Status: Expired due to Term
First Claim
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1. A method, for practice on a computer, for reasoning with uncertainty in a rule-based reasoning system comprising a plurality of rules each having a premise and a conclusion to be determined true upon finding the premise to be true, said premise comprising at least one clause including a variable to which a value can be assigned, said method comprising the steps of:

  • associating a value certainty interval with each value assigned to one of said rule premise variables, said value certainty interval having a lower and an upper bound respectively representative of amounts of confirmation and failure of refutation of the assigned value;

    associating a sufficiency factor and a necessity factor with each said rule, said sufficiency factor representing a strength of belief that the rule conclusion is true given the rule premise is true, said necessity factor representing a strength of belief that the rule conclusion is false given the rule premise is false;

    computing a premise certainty interval from the value certainty intervals respectively associated with the values assigned to the premise variables, a lower bound of said premise certainty interval being a first predetermined function of the respective value certainty interval lower bounds, an upper bound of said premise certainty interval being said first function of the respective value certainty interval upper bounds; and

    firing one of said rules by computing a conclusion detachment certainty interval having a lower and an upper bound, said conclusion detachment interval lower bound being a second predetermined function of both said rule sufficiency factor and said premise certainty interval lower bound, the conclusion detachment upper bound being a third predetermined function of both said rule necessity factor and said premise certainty interval upper bound, said conclusion detachment interval lower and upper bounds respectively representing the amounts of confirmation and failure of refutation of the rule conclusion.

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